Programming of antifuses

Abstract

The invention allows programming an antifuse so as to reduce the antifuse resistance and the standard deviation of the resistance without increasing the programming current. This is achieved by passing current pulses of the opposite polarity through the antifuse. In some embodiments, the magnitude of the second pulse is lower than the magnitude of the first pulse. Further, if the antifuse is formed on a semiconductor substrate with one electrode on top of the other electrode and on top of the substrate, the current during the first pulse flows from the top electrode to the bottom electrode and not vice versa. A programming circuitry is provided that allows to program antifuses in a programmable circuit. A driver circuit is connected to each "horizontal" channel and each "vertical" channel. Each driver circuit is controlled by data in the driver circuit. The driver circuits are connected into shift registers so that all the data can be entered from one, two, three or four inputs. No decoding circuitry is necessary. Before programming, the drivers precharge all the channels to an intermediate voltage. During programming, the channels that are not directly connected to the antifuse being programmed are switched to high impedance. As a result, the power consumption is reduced and the programming proceeds faster.

What is claimed is: 
     
       1. A method for programming an antifuse, the method comprising the steps of: generating a first current pulse through the antifuse to program the antifuse; and   generating a second current pulse through the antifuse of a polarity opposite from the polarity of the first pulse,   wherein the antifuse resistance after the second pulse is below 100 ohms.   
     
     
       2. The method of claim 1 wherein the antifuse comprises: a first electrode;   a dielectric overlaying the first electrode and having an opening therethrough;   a programmable material overlaying and contacting the first electrode in the opening;   insulating spacers around the sidewalls of the opening; and   a second electrode overlaying and contacting the programmable material.